JP3784232B2 - Stereolithography apparatus and stereolithography method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical modeling apparatus and an optical modeling method, and in particular, an optical modeling apparatus that uses a visible light source and a liquid crystal panel to optically model a three-dimensional shape of a modeling target (for example, a resin) in a non-laminated and integrated manner. And an optical modeling method.
[0002]
[Prior art]
Stereolithography technology is widely used, for example, in fields such as trial production of products or parts in the medical and industrial fields and simple mold creation for small-scale production. Expectations for higher accuracy and expansion of application fields Is growing. In addition, since the optical modeling technique is a technique used in various fields, the shape, size, and material of the target product vary.
[0003]
In general, in the development of new products such as industrial products, it is important to shorten the lead time. The product and its parts are usually designed by CAD, and it is desired to create a prototype accurately and quickly at the development stage. Conventionally, rapid prototyping by the additive manufacturing method has progressed in addition to the technology of directly cutting products or parts by machining with NC machine tools based on three-dimensional CAD data.
[0004]
There are many kinds of additive manufacturing methods such as photo-curing resin method (optical modeling method), spurious laser beam (thermosetting) sintering method, inkjet nozzle deposition method, extrusion deposition method, and method of laminating cut sheets. There is. In either method, in order to obtain a desired three-dimensional shape, a plurality of layers are stacked using three-dimensional CAD data as two-dimensional sheet-like data. In particular, in the photo-curing resin method, modeling is performed by creating two-dimensional slice data from three-dimensional CAD data, scanning a resin as a modeling object in two dimensions with a laser beam, and curing the resin.
[0005]
[Problems to be solved by the invention]
However, in the conventional additive manufacturing method, in order to improve the dimensional accuracy of a desired shaped article, it is necessary to increase the number of layers, which increases manufacturing time and cost. In addition, since the resin is sequentially cured, the accuracy may be reduced due to shrinkage during the curing. Furthermore, it is necessary to place a support on a complicated structure or a part that floats in the air and to remove it after processing.
[0006]
Further, in order to shorten the processing time and process, an optical modeling method using batch surface exposure using a liquid crystal panel has been proposed. However, since it is necessary to use ultraviolet rays, the liquid crystal may be damaged or destroyed. Further, in this stereolithography method, diffracted light and scattered light are generated, the image is unclear, and the dimensional accuracy of the modeled object is not good.
[0007]
In view of the above points, the present invention provides a stereolithography apparatus and a stereolithography method that can cover from small-sized and medium-sized modeling to micro-shaped modeling such as precision parts, micromachining products or parts. With the goal.
[0008]
An object of this invention is to implement | achieve non-stacking modeling by surface exposure with a high modeling freedom degree, high precision, and high speed using a liquid crystal mask and visible light. An object of the present invention is to facilitate intensity modulation of an exposure image by controlling a modeling depth based on a liquid crystal display gradation.
[0009]
Another object of the present invention is to provide a stereolithography apparatus and a stereolithography method suitable for high-mix low-volume production by facilitating creation of modeling data and enabling a plurality of parts having different shapes to be created simultaneously. .
[0010]
[Means for Solving the Problems]
Since the liquid crystal display can display an arbitrary image, it can be used as a variable mask, which has been difficult to produce conventionally. The main feature of the liquid crystal stereolithography method of the present invention is that this liquid crystal mask is used to perform collective surface exposure and perform modeling that does not include a beam scanning step. Since it does not include a step of creating a surface from a point by scanning, it is possible to achieve a reduction in modeling time and an increase in accuracy. In addition, since the liquid crystal can change the intensity of transmitted light by grayscale display, a three-dimensional shape can be created collectively from an image having three-dimensional information obtained by adding intensity information to a two-dimensional image. In this respect, it is very different from the conventional method in that it does not require the process that is indispensable for expansion from 2D to 3D. Furthermore, since the handling of images is easy, a new use method such as enlarging and reconstructing the shape from three-dimensional measurement data such as AFM can be considered.
[0011]
In addition, the liquid crystal may generate heat due to noise such as first-order diffracted light resulting from diffraction and light absorption / light irradiation of the liquid crystal. In the present invention, in order to suppress or prevent this, in addition to using a visible light source and a visible light photosensitive resin, measures such as removal of first-order diffracted light by a spatial frequency filter are taken.
[0012]
According to the first solution of the present invention,
A light source that outputs visible light for modeling a modeling object;
A liquid crystal mask part in which transmitted light or reflected light is controlled by two-dimensional information and gradation information;
A control unit that gives two-dimensional information and gradation information to the liquid crystal mask unit, and sets the three-dimensional shape of the modeling object;
With
Provided is an optical modeling apparatus in which a visible light from the light source transmits or reflects through the liquid crystal mask controlled by the control unit and is irradiated on a modeling target to form a three-dimensional shape. .
[0013]
According to the second solution of the present invention,
Give two-dimensional information and gradation information to the liquid crystal mask part, set the three-dimensional modeling shape of the modeling object,
Adjusting visible light from the light source to light having a predetermined beam diameter and a uniform or substantially uniform intensity distribution;
Provided is an optical modeling method in which a three-dimensional shape is formed by irradiating a modeling object with adjusted light transmitted through a liquid crystal mask part or reflected by a liquid crystal mask part.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a configuration diagram of the optical modeling apparatus of the present invention. This stereolithography apparatus includes a light source 1, a collimator unit 2, a quarter wavelength plate 3, a half wavelength plate 4, a liquid crystal mask unit 5, a lens 6, a pinhole 7, an X-Z stage 8, and a control unit (PC). 9 is provided.
[0015]
The light source 1 is various lasers that generate visible light. In this embodiment, for example, a large output can be obtained, and visible light (for example, wavelength 488 nm) is generated and the liquid crystal is not damaged (the ultraviolet light may damage the liquid crystal). A visible light source Ar + laser is used. The collimator unit 2 is configured by combining an objective lens 21, a pinhole 22, a lens 23, and the like. The collimator unit 2 widens the beam diameter from the light source 1 so that the entire LCD 52 or a wide range can be irradiated. The collimator unit 2 also serves to make the light intensity uniform throughout. The quarter-wave plate 3 converts circularly polarized light into linearly polarized light, and reduces beam energy loss at the polarizer (z) in front of the LCD 52. The half-wave plate 4 changes the polarization direction of the light converted into linearly polarized light, and converts it into a direction in which an optimum contrast can be obtained for the LCD 52.
[0016]
The liquid crystal mask unit 5 includes a polarizer (z) 51, a liquid crystal panel (LCD) 52, and a polarizer (z) 53. The polarizer (z) 51 cuts off the light of the non-linearly polarized component before entering the LCD 52 and improves the contrast of the image. The LCD 52 includes, for example, a TFT liquid crystal, displays an image output from the directly connected PC 9, converts the polarization direction for each pixel according to the display image, and sets the rotation angle of polarization to uniformly illuminated light. Give image information. The polarizer (y) 53 passes through this polarizer, and the image displayed on the LCD 52 is converted into light shading. The intensity of light corresponding to the pixel is determined by the rotation of the polarization for each pixel of the LCD 52.
[0017]
The control unit (PC) 9 gives two-dimensional information and gradation information to the LCD 52 of the liquid crystal mask unit 5, and sets the three-dimensional modeling shape of the modeling object. For example, based on the three-dimensional CAD data of the modeled object, two-dimensional slice data is created and converted into gradation data of the LCD 52 as the vertical data. By forming an image of the light that has passed through the LCD 52 on the modeling object 10, a modeling object is created by a single surface exposure for exposure using a plurality of slice data.
[0018]
The lens 6 currently uses a zoom lens and can convert image reduction and magnification. The lens 6 forms an image displayed on the LCD 52 on the modeling object 10. A mirror 61 can be provided as appropriate to adjust the direction of light. The spatial frequency filter 7 can use a pinhole, for example. The spatial frequency filter 7 cuts the diffracted light except for the zero dimension generated by the LCD 52. This prevents image degradation due to light interference at the imaging position. That is, the 0th-order light travels straight, but the other diffracted light travels in the direction that satisfies the Bragg condition. Therefore, the spatial frequency filter 7 (pinhole) is arranged at the position where the light passes through the lens and is condensed. Only the 0th order light is allowed to pass through. Further, the spatial frequency filter 7 can similarly remove the light after the second-order diffracted light. In addition, since the intensity of the diffracted light after the second order becomes weak, it is mainly the first order diffracted light that actually affects.
[0019]
The X-Z stage 8 accurately arranges the position of the modeling object 10 on the surface on which the image is formed by the lens. The base plate 81 actually arranges the modeling object 10. A transparent, thin glass or plastic plate is used because it is exposed to light from below. Here, as an example, a cover glass having a thickness of 150 μm was used. For example, a photocurable resin is used for the modeling object 10. Here, as an example, a photocurable resin specially prepared so as to have sensitivity to visible light is used, and its peak sensitivity is adjusted to around 488 nm. The modeling object 10 is not limited to this, and an appropriate material that can be modeled by the light source 1 can be used.
[0020]
The operation of the optical modeling apparatus and method of the present invention will be described below.
In this example, Ar + laser (λ = 488 nm) is used as the light source, and the beam diameter is enlarged by the collimator unit 2 to be incident light. Incident light having a uniform intensity distribution after passing through the quarter-wave plate 3 and the half-wave plate 4 is transmitted through the liquid crystal mask portion 5 and then passed through the lens 6 to be converted into first-order diffracted light by the spatial frequency filter 7. Noise can be removed. The liquid crystal image is reduced (for example, 9/25) and formed on the base plate 81 by the operation of the reduction optical system such as the lens 6. A visible light curable resin is disposed on the base plate 81 as the modeling object 10, and the material is cured without being laminated.
[0021]
Below, the example of modeling object creation by this invention is demonstrated.
As an example of the LCD 52, a TFT active matrix type pixel number of 800 × 600 pixels, a screen size of 26.40 × 19.98 mm, a pixel size of 33 × 33 μm, and the like were used. The light source 1 is an argon (Ar +) laser (wavelength 488 nm, linearly polarized light, 100 mW to 1.5 W). The light intensity was 300 mW and the exposure time was 2 to 10 sec. The resin used for the modeling object 10 was urethane acrylate.
[0022]
FIG. 2 is an explanatory diagram of the light transmittance of the liquid crystal. This shows that about 70 gradations can be used for intensity modulation. It can also be seen that the LCD 52 has a light shielding performance close to 100%. As measurement conditions, light is incident on the LCD 52, and only the intensity of the 0th-order light can be mainly measured.
[0023]
FIG. 3 is an explanatory diagram showing the relationship between display gradation, light intensity, and curing depth.
This figure shows the relationship between the display gradation (color density) of the liquid crystal, the light intensity, and the curing depth. The curing depth is almost proportional to the logarithm of irradiation energy according to Lambert-Beer's law. Therefore, it is estimated from the figure that the curing depth is substantially proportional to the display gradation. Several basic shapes were prototyped in order to confirm the relationship between display gradation and curing depth. The results shown here are all created by a non-lamination process.
[0024]
FIG. 4 shows an image used for the liquid crystal mask. In FIG. 5, the figure of the shape shape | molded by each liquid crystal mask is shown.
The reason why the scales are different in both figures is that the liquid crystal image is reduced. In each figure, (a) is an open alphabet, (b) is a square whose gradation changes equidistantly toward the center, and (c) uses 3D measurement data of lattice fringes by AFM. . The modeling conditions are, for example, an incident light intensity of 500 mW and exposure times of 1 second, 4 seconds, and 4 seconds, respectively. As a result, two-dimensional shape modeling, three-dimensional shape modeling, and the possibility of shape restoration from three-dimensional measurement data were confirmed.
[0025]
FIG. 6 is an explanatory diagram of the cured shape measured in a non-contact manner by the optical ring displacement sensor. In the figure, (a) shows the measurement result of the character shape. (B) in the figure shows the measurement result of the quadrangular pyramid shape, the oblique viewpoint and the front profile. For the optical ring type displacement sensor, see, for example, Hirohiro Takatani et al .: Research on non-contact stereolithography 3D shape measurement, Academic Lecture Meeting of the Japan Society for Precision Engineering (1996) 559, etc. In particular, it can be seen from the cured shape of the quadrangular pyramid as shown in (b) in the figure that the relationship between the gradation and the cured depth is in good agreement with the estimated value shown in FIG. From these results, it was confirmed that the curing depth changed almost in proportion to the gradation.
[0026]
FIG. 7 shows another image (upper) used for the liquid crystal mask and an SEM observation image (lower). In the figure, (a) shows the alphabet, and (b) shows the tube. Here, the exposure time is 4 seconds. In this way, it can be confirmed that three-dimensional modeling is performed.
[0027]
FIG. 8 is a diagram showing an input image and an SEM observation image for multi-product simultaneous production. Multiple gears were formed with an exposure time of 4 seconds and a gear thickness of 1 mm. The production time was about 1/10 of the conventional time.
[0028]
As described above, a prototype of a shape was made according to the present invention, and it was confirmed that a three-dimensional shape could be freely formed in a non-stacked manner from the relationship between the curing depth and the display gradation. In addition, it was confirmed that the present invention enables restoration of three-dimensional measurement data and high-precision modeling.
[0029]
In addition, in this invention, it can be set as the reflection-type optical modeling apparatus and method of reflecting incident light from a light source and irradiating a modeling target object by providing a reflective part or a reflective mirror in a liquid crystal panel. . In the above-described embodiment, the specifications such as the wavelength used, the size of the liquid crystal mask and the number of pixels, the material / shape / size, etc. of the object to be modeled are merely examples, and may be changed or modified as appropriate. Can do.
[0030]
【The invention's effect】
According to the present invention, as described above, it is possible to provide an optical modeling apparatus and an optical modeling method capable of covering from small-sized and medium-sized modeling to micro-shaped modeling such as precision parts, products or parts for micromachining. Can do.
[0031]
According to the present invention, intensity modulation of an exposure image can be facilitated by controlling the modeling depth based on the liquid crystal display gradation. According to the present invention, using a liquid crystal mask and visible light, non-laminated modeling by surface exposure can be realized with high modeling freedom, high accuracy, and high speed.
[0032]
According to the present invention, it is possible to provide a stereolithography apparatus and a stereolithography method suitable for high-mix low-volume production by facilitating creation of modeling data and simultaneously creating a plurality of parts having different shapes.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an optical modeling apparatus of the present invention.
FIG. 2 is an explanatory diagram of light transmittance of liquid crystal.
FIG. 3 is an explanatory diagram regarding the relationship between display gradation, light intensity, and curing depth.
FIG. 4 is a diagram of an image used for a liquid crystal mask.
FIG. 5 is a diagram of a shape formed by each liquid crystal mask.
FIG. 6 is an explanatory diagram of a cured shape measured in a non-contact manner by an optical ring type displacement sensor.
FIG. 7 is a diagram showing another image used for the liquid crystal mask and a SEM observation image.
FIG. 8 is a diagram showing an input image and an SEM observation image for multi-product simultaneous production.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light source 2 Collimator part 3 1/4 wavelength plate 4 1/2 wavelength plate 5 Liquid crystal mask part 6 Lens 7 Pinhole 8 X-Z stage 9 Control part (PC)
10 Modeling object

Claims (5)

A light source that outputs visible light for modeling a modeling object;
A collimator that widens the beam diameter of the light from the light source and equalizes the light intensity;
A quarter-wave plate for converting circularly polarized light from the collimator into linearly polarized light and reducing beam energy loss in the polarizer;
A half-wave plate for changing the polarization direction of light converted to linearly polarized light from the quarter-wave plate;
A liquid crystal mask part in which transmitted light or reflected light is controlled by two-dimensional information and gradation information;
Said the liquid crystal mask portion, two-dimensional information, and a control unit for setting the three-dimensional shape of the shaped object by applying a gradation information substantially proportional to the shaping depth of the shaped object,
With
The liquid crystal mask part is
A liquid crystal panel that displays grayscale images based on the two-dimensional information and gradation information output from the control unit, converts the polarization direction of light for each pixel according to the display image, and provides image information as a rotation angle of polarization;
A first polarizer for cutting a nonlinear polarization component of light incident on the liquid crystal panel and improving an image contrast;
A second polarizer for determining an intensity of light corresponding to the pixel by rotation of polarization for each pixel of the liquid crystal panel, and converting an image displayed on the liquid crystal panel as light shading;
Have
Visible light from the light source is transmitted or reflected through the liquid crystal mask controlled by the control unit, and an image displayed in gray on the liquid crystal panel is irradiated to the modeling object through the second polarizer. Thereby, the optical modeling apparatus which modeled the said three-dimensional shape by the non-lamination by surface exposure . Wherein the light transmitted through or reflected by the liquid crystal mask portion, the optical modeling apparatus according to claim 1, further comprising a spatial frequency filter for cutting the diffracted light other than zero-order light. Shaped object, the optical modeling apparatus according to claim 1 or 2, characterized by using a photocurable resin. A liquid crystal panel, two-dimensional information, and sets the three-dimensional shape of the shaped object by applying a gradation information substantially proportional to the shaping depth of the shaped object,
Adjust visible light from the light source to light with a predetermined beam diameter and uniform or substantially uniform intensity distribution,
Convert the adjusted circularly polarized light into linearly polarized light,
Change the polarization direction of the light converted to linearly polarized light,
Cut the non-linear polarization component of the light whose polarization direction has been changed, enter the liquid crystal panel,
The liquid crystal panel displays a grayscale image based on the given two-dimensional information and gradation information, converts the polarization direction of light for each pixel according to the display image, and gives image information as a rotation angle of polarization,
The intensity of light corresponding to the pixel is determined by the rotation of polarized light for each pixel of the liquid crystal panel, and the image displayed on the liquid crystal panel is converted as light shading,
Visible light from the light source is transmitted or reflected through the liquid crystal panel, and the image displayed on the liquid crystal panel is converted into light shading and irradiated on the object to be modeled. An optical modeling method in which modeling is performed by lamination. The optical modeling method according to claim 4 , wherein the light transmitted through or reflected by the liquid crystal panel is further passed through a spatial frequency filter to irradiate the modeling object.

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